Highway crossing signal control systems



March 17, 1953 J. E. MCMAHON, JR ,0

HIGHWAY CROSSING SIGNAL CONTROL SYSTEMS Filed July 15, 1950 I) -5 1% "r- 4 I j I r I I lb BT11 w r- 50 mm 51 11:4 M ni 5 mail [2 INVENTOR 11/5 ATTORNEY Patented Mar. 17, 1953 HIGHWAY CROSSING SIGNAL CONTROL SYSTEMS James E. McMahon, Jr., Penn Township, Allegheny County, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application July 15, 1950, Serial No. 173,979"

4 Claims.

My invention relates to a highway crossing signal control system of the type adapted to provide protection for both directions of railroad trafiic on a stretch of single track. More particularly my invention relates to a system of the above described type which is arranged to provide for proper operation should the track become shunted by a highway vehicle at the crossmg. 7 V

A highway crossing signal control system automatically initiates operation of a highway crossing signal when a train approaches an intersection, and customarily discontinues such operation only when the train has cleared the crossing. On a stretch of single track intersected by a highway, protection of this type must be provided for both directions of railroad traflic if trains are to move over the track in either direction. Where track circuits are employed, it is usual in such cases to provide a crossing section which includes the intersection and two approach sections located one on each side of the intersection adjoining the crossing section. Apparatus is then provided to initiate operation of the signals when a train travelling toward the intersection in either direction enters an approach section, and to terminate operation when the train vacates the crossing section.

One form of apparatus that has been proposed heretofore for accomplishing this result contemplates the use of an interlocking relay to control the signals, and a track circuit including a track relay for each track section to control the interlocking relay. The interlocking relay has two windings, each provided with an armature, and an interlocking mechanism which on the release of either armature latches up the other armature to prevent it from closing its back contacts if it should release before the first armature is picked up. The'system is arranged to provide'for the deenergization of one winding of this interlocking relay when the track relay of one approach section is released, for the deenergization of the other winding when the track relay of the other approach section is released, and for the deenergization of both windings when the track relay of the crossing section is released. The desired protection is then obtained by controlling the signals over back contacts of the. interlocking relay such that the signals are set-into operation whenever one armature of the interlocking relay. has closed its back contacts.

Although apparatus of the above described type will normally function in the desired manner,

any system so arranged has an inherent difficulty in that proper operation of the signals may be interfered withwhen the track circuit of vthe crossing section is shunted by a crawlertype ractor or similar vericle moving across the tracks. When the track circuit of the crossing section is shunted through the metallic treads and body of the vehicle both windings of the in-. terlocking relay are deenergized and it is indeterminate as to which of the armatures shall close its back contacts and which shall be latched up. Although the signals will operate under these conditions whichever armature is closed, if the back contacts controlled by the armature of one approach section should close and a. train then enters the other approach section the signals will cease to operate when the highway vehicle ceases to shunt the rails of the crossing section and will not operate as the train proceeds through the intersection.

To obviate this difficulty it has been proposed to utilize two interlocking relays, one for each approach section, and a track relay for the crossing section. Each interlocking relay has a first winding connected in a track circuit for its associated approach section so as to be responsive to trafiic in that section. The second windingsoi the interlocking relays are controlled by the track relay and by the windings of the interlocking relays in such a manner that when a train travels the stretch including the crossing the windings are released in the sequence necessary to establish the proper directional control of the signal for that train. In one such system that has been proposed, the control of the second windings is such that if the approach sections vacant the track relay of the crossing section is shunted in response to a highway vehicle at the crossing, the second windings are held energized so as to avoid creating a condition which would tend to latch up either first winding if a train should enter an approach section under these conditions. Such a system is disclosed and claimed in a copending application for Letters Patent of the United States, Serial -No. 144,823, filed on February 17, 1950, by Otto W. Rost and assigned to the assignee of the present application.

My invention provides another such system characterized in that the second windings of the interlocking relays arecontrolled in such a manner that the two second windings are released whenever a train occupies the crossing section and are picked up in normaloperation whenever a train vacates the crossing section, but

if a highway vehicle shunts the crossing section with both approach sections vacant, the second windings pick up when the highway vehicle moves oif the rails of the crossing section, only if both approach sections are still vacant. The apparatus embodying my invention provides this control of the two second windings of the interlocking relays by circuits which are operated on the closed circuit principle so that any failure of these circuits to function properly will result in a safe failure of the system.

It is an object of my invention to provide a system of the above described type incorporating control circuits for the second windings of the interlocking relays arranged on the closed circuit principle.

Another object of my invention is to provide a system of the type mentioned for retaining the second windings of the interlocking relays released at times to provide for operation of the crossing signals.

A further object of by invention is to provide a .novel and improved highway crossing signal control system of the type described.

Other important objects and characteristic features of my invention will become apparent from the following description.

In attaining the above mentioned and other important objects of my invention I provide in a system of the type described, a control circuit for the two second windings of the interlocking relays, which circuit is responsive to traffic in the crossing section and includes the two second windings in series, and is completed through one or another of a plurality of alternate paths, one constituting a pickup path including in series front contacts of the two first or traffic responsive windings of the interlocking relays, and another two paths .respectively including a fiagman contact of the two second windings and consequently having stick circuit functions.

The apparatus of my invention is an improvement over that which is disclosed in the copending application Serial No. 144,823, filed February 17, 1950, by Otto W. Rost, for Highway Crossing Signal Control Systems.

I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view of one form of apparatus embodying my invention.

Referring now to the drawing, the reference characters I a and 'lb designate the rails of a given stretch of track over which traffic may move in either direction and which as shown is intersected at grade by a highway H. A highway crossing signal designated by the reference character XS and which may take any one of a number of suitable forms but which is represented as the flashing light type in the drawing, is located adjacent the intersection. The signal is-controlled by an operating relay SR which may be of the flasher relay type illustrated in the drawing.

The flasher relay SR is characterized by the provision of two coils permanently connected in series, an armature mounted for attraction to either coil, and contacts operated between extreme right and left-hand positions depending upon the position of the armature. When contact 26 is in its left-hand position it establishes a-shunt path around the left-hand coil of the relay,-and when in its right-hand position it establishes-a shunt'around the right-hand coil. When the relay is deenergized the armature is biased to one of its extreme positions, for example, the left-hand position as shown in the drawing to assure a starting action so that when the relay is energized, the right-hand winding is first effective to create a flux which attracts the armature to its right-hand position and contact 26 thereupon shunts the right-hand coil, whereupon the left-hand coil operates to attract the armature and the armature is alternately operated between its two extreme positions. The armature carries another contact 21 through which energy is supplied to the signal lamps. A relay of this type is shown, for example, in Letters Patent of the United States, Reissue No. 17,252, dated April 2,

1929, to C. S. Snavely and W. B. Wells.

The track rails Ia and ID are divided by insulated joints 2 into an approach section AT located on one side of the crossing, a crossing section BT including the intersection of the highway with the stretch, and an approach section CT on the other side of the crossing. Each such section is provided with a track circuit including a track battery 3. The track circuits for sections AT and CT include windings 30 and 33, respectively, of interlocking relays WXR and EXR. The track circuit for section BT includes the winding of a track relay BTR.

Interlocking relays WXR and 'EXR are each characterized by the provision of a mechanical locking arrangement which for relay WXR is controlled by the armatures of windings 30 and 3| and for relay EXR. is controlled by the armatures of windings 32 and 33. When both armatures of either relay are picked up, the release of one will latch up the other to prevent its back contacts from closing if it should release before the first armature has picked up. One winding of each interlocking relay is provided with a flagman contact conventionally represented in the drawing. Such a contact is one which does not open when its armature releases to a latched up position. The other winding is provided with an ordinary front contact which does open when its armature releases to a latched up position. Thus, taking relay WXR as an example, if winding 30 is the first to be released, its front contact I0 will open and its back contacts II and I2 will close, but the armature of winding 3| will be latched up so that when winding 3| subsequently becomes deenergized with winding 30 still released, its front contact I3 which is a flagman type contact will be prevented from opening and its back contacts I4 and I5 will be prevented from closing. Similarly, if it is assumed that winding 3| is the first to be released, it will when it releases open its flagman contact I3, close its back contacts I4 and I5, and latch up the armature of winding 30. When winding 30 subsequently becomes deenergized its front contact It] will open but its back contacts I I and I2 will be prevented from closing. A relay having an interlocking mechanism capable of affording this operation is shown, for example, in Letters Patent of the United States No. 1,799,629, granted April 7, 1931, ,to W. K. Lockhart and T. J. OMeara.

The windings 3| and 32 are controlled by a circuit responsive to traffic in section BT, are released whenever section ET is occupied and are picked 'up whenever section BT becomes vacant provided either that one winding 3| or the other winding 32 is latched up to hold closed its flagman contact I3 or 20, respectively, or that both windings 30 and 33 are picked up to close their front contacts l and 23, respectively. The circuit for the two windings 3i and 32 of relays WXR and EXR may be traced from terminal B through front contact l6 of relay BTR the winding 3i of relay WXR and three alternate paths one including fiagman contact l3 of winding 3| the second including fiagman con tact 23 of winding 32 and the third or pick up path including in series front contacts i3 and 23 of windings 39 and 33, respectively; and thence through winding 32 of relay EXR and front contact I! of relay BTR to the other terminal C. The terminals B and C are opposite terminals of a suitable source of current, such as a battery not shown. Obviously, the necessary control of windings 3i and 32 can be provided even if relay BTR should be dispensed with, in which case the terminals of windings 3| and 32, shown connected to contacts l6 and i! of relay BTR, would instead be connected across the rails la and lb.

Flasher relay SR is energized and set into operation over an obvious circuit which may be completed at back contact of winding 3|), back contact M of winding 3|, back contact N3 of relay BTR, back contact 2| of winding 32 or back contact 23 of winding 33. The two lamps of the signal are alternately energized over a circuit hereinafter traced and which circuit may be completed upon the closure of backcontact l2 of winding 38, back contact I of winding 3i, back contact IQ of relay BTR, back contact 22 of inding 32 or back contact 25 of winding 33.

The apparatus embodying my invention is illustrated in the drawing in the normal condition that obtains when the sections are unoccuni d. In this condition of the a paratus both windings of each interl cking relay are energired and track relav BTR is picked up. As a re ult flasher relav SR is deenergized and the signal is disconnected from the source of power.

When an eastbound train, that is a train operating from left to ri ht as viewed in the drawing enters section AT, the shunting action of its wheels and axles deprives windin 39 of interlocking relay WXR of current. Front contact l0 opens and back contacts H and .92 close in response. Back contact I! closes to complete the obvious energiwing circuit for flasher relay SR previouslv mentioned and relav SR responds by alternately operating its contact 21 first to one position and then to another to cause the two lamps of signals XS to be ener ized alternatelv. one over a circuit which extends from terminal B over back contact l2 of winding 33 and contact 2'! of flasher relay SR in its lefthand. position throu h the filament of one lamp of signal XS to terminal C. and the other over a circuit which extends from terminal B over back contact |-2 of winding 39 and contact 2'! of flasher relay SE in its right-hand position throu h the filament of the other lamp of signal XS to terminal C. Front contact ill of winding 33 performs no useful function at this time. but as will be made clear hereinafter is provided to assure proper control of windings 3| and 32 of interlocking relays WXR and EXR, respectively, in the event the track section at the crossing is shunted by a vehicle moving across the tracks when a train enters section AT.

When the train enters section BT, track relay BTR releases and its back contacts l8 and VI!) close to complete energizing circuits for the flasher relay SR and the signal XS, which cir-' puits insure that the signal will maintain its operation after the train vacates section AT and winding 3|] picks up to open its back contacts II and I2. Front contacts l6 and ll of relay BTR open the control circuit for windings 3| and 32 which now release. Flagman contact 28 of winding 32 opens and back contacts 2| and 22 of winding 32 close, but the fiagman and back contacts of winding 3| do not open or close respectively, because of the prior release of winding 30 which permits the armature of winding 35 to drop to a latched up position only. By remaining closed, fiagman contact I3 of winding 3| provides for the energization of windings 3| and 32 when the train vacates section BT, as will be pointed out in more detail hereinafter.

When the train enters section CT winding 33 of relay EXR releases to its latched up position, and its back contacts 24 and 25 are therefore held open.

As the train vacates section AT winding 30 of relay WXR picks up, its front contact I0 closes and its back contacts II and I2 open. Windings 3i and 32 are unaffected when front contact is closes, since front contacts l6 and I! of relay BTR. are open to maintain windings 3| and 32 released, nor is the signal affected when back contacts H and I2 open, since energizing circuits for the flasher relay and the signals are still closed at back contacts I8 and H] of relay BTR and back contacts 2| and 22 of winding 32.

When the train vacates section BT, relay BTR picks up closing its front contacts l6 and I1 and in response windings 3| and 32 pick up, since the control circuit of these windings including fiagman contact i3 of winding 3| is now completed at front contacts is and I! of relay BTR. With track relay BTR and wind ings 3i and 32 picked up, the flasher relay and the signal are now disconnected from the source of power and the signal therefore ceases its operation.

When the train vacates section CT, winding 33 of relay EXR picks up, its front contact 23 closes, and its back contacts 24 and 25 assume their picked up position restoring the apparatus to its normal condition.

The equipment operates in a substantially corresponding manner for westbound traffic as it does for eastbound traffic, and further detailed description of its operation is therefore believed unnecessary except to point out that for westbound train movement, winding 32 will be released after winding 33 has dropped to its full released position, and winding 32 in its latched up position retains fiagman contact 20 closed so that after the train vacates section ET the two windings 3i and 32 will be picked up over the circuit path including fiagman contact 29. It follows that fiagman contact 20 pro-'- vides a pick up circuit for the two windings 3| and 32 for a westbound train in a manner corresponding to that effected by fiagman contact E3 of winding 3! in providing in its latched up position a pick up circuit for the two windings 3! and 32 for an eastbound train.

It follows from the foregoing description of the operation of the apparatus shown in the drawing that my invention is effective to provide proper operation of the signal for a train operating in either direction on the stretch including the crossing. In addition, the apparatus 15 arranged to assure operation of the signal to provide protection for the crossing for a train approaching the crossing should the train en t a p oa h s ct du in t e t m h a highway vehicle moving across the tracks shunts the trackcircuitof the crossing section.

If, for example, with sections AT, BT and CT vacant acrawler type tractor .or similar vehicle shunts the track circuit at the crossing, track relay B'IiR will release, its front contacts 16 ,and J1 will .open and its back contacts i8 and I9 willclose. When back contacts l and 19 close the signal is set into operation. Front contacts l6 and l] of relay BTR open the control circuit for windings 3| and 32 of relay WRX and .EXR, respectively, .causing them to release, whereupon .fiagman contact [3 .of winding 3| and flagman contact 23 of winding 32 open, and backcontacts J4 and I5 of winding 3| and back contacts 2| and 22 of winding 32 close. With fiagman contacts 13 and both open, windings 3l a-nd 32 can be picked up after relay BTR picks up to close its frontcontacts i6 and ii, only if .both windings 3i and .33 are picked up so that their respective front contacts is and 23 are closed to provide a pick up circuit for the windings 3| and32.

If the highway vehicle clears the rails before a train .enters either approach section relay B'IR will pick up and in turn windings and 32 will become energized over the alternate circuit path including front contacts it; and 23 of windings and 33, with the result that operation of flasher relay SR and signal XS is terminated andthe apparatus is restored to normal. If, however, a train should enter either approach section while relay BTR is shunted by a highway vehicle at the crossing, relay BTR willthen pick up when the highway vehicle clears the rails but both windings 3i and 32 will remain released. For example, if an eastbound train enters section AT while section ET is shunted by a highway vehicle so that relay BTR and windings 3| and 32 are released, winding 30 of relay WXR releases and its front contact It] opens to insure the continued deenergization of windings 3| and 32 when relay BTR subsequently picks up to close its front contacts l8 and IT. Back contacts H and 52 of winding 33a1'e prevented from closing because of the prior release of winding-3| of relay WXR. When the highway vehicle ceases to shunt the track circuit at the crossing relay BTR, picks up closing itsfront contacts I5 andi'l and opening its back contacts i8 and IS. The control circuit for windings 3| and 32 is however held open at front contact In of winding 32: and fiagman contacts l3 and 2 ii of windings Si and 32, respectively, so that these windings remain released eventhough front contacts 53 and H of relay BTR. are closed. Back contacts i3 and IS in opening do not affect the operation of the signal since energizing circuits for the sig nal and the flasher relay are still complete at back contacts M and I5 of winding 3| and'bacl: contacts 2| and 22 of winding 32.

When the train enters section ET relay BTR releases once again to open its front contacts Hi and l! and close its back contacts is and i9; however, these contacts perform no useful function at this time.

As the train enters section CT winding of relay EXR releases and its front cont-act 23 opens, but back contacts 2 1 and :25 of winding 33 remain open because of the prior release of winding 32.

As the train ,vacates section AT, winding 33 of relay WXR picks up to restore its contacts to their normal position. .Front contact In of winding 3i] closes and back contacts II and I2 of winding 30 are brought from a latched up position to their picked up position.

When the train vacates section BT front contacts l6 and H of relay BTR close and back contacts 8 and IQ of relay BTR open. Front contacts It and lldo not affect the energization of windings 3| and 32 since the circuit which controls their operation is still open at flagman contact .|3 of winding 3|, fiagman contact 20 of winding 32 and front contact 23 of winding 33, nor do back contacts I8 and I9 affect the operation of the signal for back contacts I4 and ,li of winding 3| and back contacts 2| and 22 of winding 32 remain closed to continue the signal in operation.

When the train vacates section CT winding 33 picks up and-its front contact 23 closes to complete the previously mentioned pick up circuit of windings 3| and 32 including front co ntact ID of winding 30 and-front contact 23 of winding 33. .Windings 3| and 32 pick up closing flagmancontacts v|3 and 20 of windings 3| and 32, respectively, and opening back contacts H and i5 of winding 3| and back contacts 2| and 22 of winding 32. Operation of the flasher relay and crossing signal are now terminated, and the apparatus is once again in its normal condition, that is, the condition which normally obtains when each of the track sections employed is vacant. Similarly, the equipment will operate in a substantially corresponding manner should a west bound train enter section CT while the track circuit at the crossing is shunted by a highway vehicle moving across the tracks.

From the foregoing description it is apparent that windings 3| and 32 are controlled over a circuit which is responsive to traflic in section BT, and that both windings are released whenever section BT is occupied but that both are picked up when section B'I becomes vacant only if one or the other of windings 3| and 32 is latched up to hold flagman contact |3 or 20 closed or if both windings 30 and 33 are picked up .to close their front contacts 10 and 23, respectively. This circuit arrangement is effective to provide for the proper operation of the signal for a train travelling in either direction on the stretch including the crossing, and is also effective to assure operation of the signal to provide protection for the crossing in the event a train approaching the crossing should enter an approach section while the track circuit of the crossing section is shunted by a highway vehiclemoving across thetracks. Further-more, protection at the crossing for a train which enters an approach section when the track circuit of the crossing section is shunted by a highway vehicle moving across the tracks is obtained by a circuit arranged on the closed circuit principle and the failure of any circuit element will tend to open the circuit to release windings 3| and 32, one or the other or both of which when released cause signal XS to be set into operation. Windings 3| and 32 cannot be latched up at the same time under any traffic conditions so that a failure of circuit results in operation of the signal to provide a safe failure.

Although I have illustrated and described only one form of highway crossing signal control system embodying the features of my invention, it is to be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a stretch of railway track intersected by a highway, a first, a second and a third. section in said. track stretch with said first and said third sections located on opposite sides of the crossing, and with said second section including the crossing, a signal for said intersection, a track circuit for said second section, a track relay included in said track circuit, an interlocking relay for said first section, an interlocking relay for said third section, a first winding for the interlocking relay of said first section controlled by the presence of a train in said first section, a first winding for the interlocking relay of said third section controlled the presence of a train in said third section, a second winding for the interlocking relay of the first section, a second winding for the interlocking relay of said third section, circuit means connecting said second windings in series jointly controlled by said track relay and ineluding three parallel paths a first one of which is controlled by the second winding of the interlocking relay for said first section and a second one of which is controlled by the second winding of the interlocking relay for said third section and the third one of which is controlled by the first winding of the interlocking relay for said first section and by the first winding of the interlocking relay for said third section,

and other circuit means responsive to the operation of said interlocking relays and said track relay to control the operation of said signal.

2. In combination, a stretch of railway track intersected by a highway, a first, a second and a third section in said track stretch with said first and said third sections located on opposite sides of the crossing, and with said second section extending over the crossing, a signal for said intersection, a track circuit for said second section, a track relay included in said track circuit, an interlocking relay for said first section, an interlocking relay for said third section, a first winding for the interlocking relay of the first section controlled by the presence of a train in said first section, a first winding for the interlocking relay of the third section controlled by the presence of a train in said third section, a second winding for the interlocking relay of the first section, a second winding for the interlocking relay of the third section, a control circuit connecting said second windings in series extending over a front contact of said track relay, a front 10 contact of each of said first windings or a fiagman contact of either of said second windings, and circuit means responsive to the operation of said interlocking relays and said track relay to control the operation of said signal.

3. A highway crossing signal control system for a stretch of single track railway intersected at grade by a highway and divided into three successive adjoining track sections the middle one of which includes the intersection, said system including a highway crossing signal at said intersection, a track relay, a track circuit including said track relay for said middle section, interlocking relay means having first and second windings, means for controlling said first windings of said interlocking relay means by trafiic on the two outer track sections, means for controlling said highway crossing signal by said track relay and said first and second windings of said interlocking relay means, and means governed jointly by said track relay and by means controlled by both of said first windings in multiple with means controlled by each of said second windings for controlling said second windings of said interlocking relay means such that said second windings release when the track circuit of said middle section is shunted while the outer sections are both vacant and then pick up when the shunt is removed only if the outer sections are both vacant.

4. A highway crossing signal control system for a stretch of single track railway intersected at grade by a highway and divided into three successive adjoining track sections the middle one of which includes the intersection, said system including a highway crossing signal at said intersection, two interlocking relays one for each outer track section and each having a first and a second winding, means for controlling the first winding of each interlocking relay by traific in its respective outer track section, means for controlling said highway crossing signal by said first and second windings of said interlocking relays, and a circuit for said second windings jointly controlled by tramc in said middle section and by means controlled by both of said first windings in multiple with means controlled by each of said second windings.

JAIVIES E. MCMAI-ION, J R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Henry et a1 Aug. 7, 1934 

